Carcinogenicity, contaminant

It is, therefore, important to realize that the incidence of cancer in man today reflects exposure of 15 or more years ago similarly, any increase of carcinogenic contaminants in man s environment today will reveal its carcinogenic effect some 15 or more years from now. For this reason it is urgent that every effort be made to detect and control sources of carcinogenic contamination of the environment well before damaging effects become evident in man. Similar concepts may apply to the need for evaluation of other chronic toxicity hazards. Environmental cancer remains one of the major disease problems of modern man. 

The EPA makes decisions about clean-up of abandoned hazardous waste sites under the so-called Superfund law. Risk assessment outcomes are one guide to the decision process. The agency has declared that, for carcinogenic contaminants, clean-up must reach lifetime risks somewhere in the range of one in 10 000 to one-in-one million most decisions seem to aim at risks of one in 100 000 or lower. Hazard index values for non-carcinogens are not expected to exceed one. Costs and technical feasibility figure heavily in these decisions. 

Figure 12.11—Comparison of UV andfluorescence detection after chromatographic separation. Aflatoxins, which are carcinogenic contaminants present in certain batches of grain cereals, are controlled by HPLC analysis. It can be seen that the peak intensities in UV detection vary with concentration whereas fluorescence detection is much more sensitive to aflatoxin G2 and B2. (Reproduced by permission of SUPELCO.)...

To illustrate the use of the recommended method, consider the reduction of N, N-nitroso-dimethylamine (NDMA), a mutagenic and carcinogenic contaminant that has been subject to considerable study (11). Reduction can occur at the N-N bond (Equation 1), or at the N-O bond (not shown). 

Figure 11.12 Comparison, following a chromatographic separation, of UV and fluorescence detection. Aflatoxins, which are carcinogenic contaminants present in certain hatches of grain cereals, are the subject of analysis by HPLC. Detection by fluorescence is much more sensitive to Gj and B2 than with UV detection (reproduced courtesy of SUPELCO). Below left, schematic of the different components of a LC-detector based upon fluorescence. This detector is able to find rapidely, for each compound eluted, the best coupling of excitation/emission without interrupting the chromatography underway (reproduced courtesy of a document from Agilent Technologies).

Another type of effects monitoring, monitoring for neoplasia in aquatic organisms, has grown out of concern over the presence of potentially carcinogenic contaminants in water. Although isolated observations of neoplasia in fish and invertebrates have been reported in the literature for many years (5J), it is only recently that programs have been developed specifically to monitor neoplasia in relation to water pollution. In the chemically polluted Buffalo Harbor, Buffalo,... 

Tumor promoter Carcinogenic contaminants Tumor promoter ... 

A large number of polycyclic aromatic hydrocarbons are known Many have been synthesized m the laboratory and several of the others are products of com bustion Benzo[a]pyrene for example is present m tobacco smoke contaminates food cooked on barbecue grills and collects m the soot of chimneys Benzo[a]pyrene is a carcinogen (a cancer causing substance) It is converted m the liver to an epoxy diol that can induce mutations leading to the uncontrolled growth of certain cells... 

Polycychc aromatic hydrocarbons (PAHs) are carcinogens produced by the thermal breakdown of organic materials. These are widely distributed in both food and the environment, and are some of the principal carcinogens in cigarette tar and air pollution. Of over 20 PAHs isolated, benzopyrene and quinoline compounds are the most commonly encountered in foods, particularly those which are broiled or fried (111). Shellfish living in petroleum contaminated waters may also contain PAHs (112). 

A comprehensive search (295) of the STORET water quaUty database, maintained by the U.S. EPA Office of Water, is used to evaluate the potential water quaUty implications of various herbicides. This database contains information on contamination of surface water (SW) and groundwater (GW) suppUes. The data are provided to give a general impression of the occurrence of a given herbicide in SW and GW (269). The U.S. EPA scheme for categorizing a chemical s carcinogenic potential is used for herbicides for which healthy advisory information (HA) is available. The U.S. EPA is continually issuing HAs for various environmental contaminants HAs available in Reference 269 were used in preparation of this article. 

Ethylene dibromide is a suspected human carcinogen and worker exposure by all routes should be carefiiUy controUed to levels as low as reasonably achievable (67). Ethylene dibromide causes severe blistering of the skin if contact is prolonged. Eye contact with the Hquid will cause pain, irritation, and temporary impairment of vision. Recommended safety equipment includes safety goggles, a NIOSH approved canister-type gas mask for organic vapors, neoprene gloves, and neoprene overshoes. In case of contact with ethylene dibromide, contaminated clothing and shoes should be removed and eyes or skin washed with plenty of water for at least 15 minutes. Contaminated clothes should be washed before reuse and contaminated shoes should be discarded. 

Chemical Contaminants (Carcinogens) If there is evidenee that a chemical may cause eancer, and there is no dose below which the chemieal is considered safe, the MCLG is set at zero. If a chemieal is carcinogenie and a safe dose can be deter mined, the MCLG is set at a level above zero that is safe. 

The process illustrated in Figure 4.6 was developed to production scale with a capacity of 200,000 tonnes per year. This process, developed by British Petroleum, was one of several in Europe and Japan that, although fully developed, was never operated substrate commercially. This was due to sharply increased substrate costs in 1973 and political costs and social pressures against the use of petroleum-based substrates (possibly contaminated with carcinogenic or toxic compounds). Such systems do operate in the former USSR, producing Candida guilliermondii as feed. 

Dioxins are prominent members of the class of polychlorinated hydrocarbons that also includes diben-zofuran, biphenyls and others. Dioxins are highly toxic environmental contaminants. Like others small planar xenobiotics, some dioxins bind with high affinity to the arylhydrocarbon (Ah) receptor. Dioxins activate the receptor over a long time period, but are themselves poor substrates for the enzymes which are induced via the Ah-receptor. These properties of the dioxins and related xenobiotics may be important for the toxicity of these compounds. Dioxins like 2,3,7,8-tetrachloro-p-dibenzodioxin can cause persistent dermatosis, like chloracne and may have other neurotoxic, immunotoxic and carcinogenic effects. 

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